supergirl-cbsComic book heroes have already taken over movie houses and have been slowly proliferating on TV, mostly due to a couple of successful superhero shows on The CW, “Arrow” and “The Flash.”

Now it’s moving to the august confines of the Viacom flagship CBS as well with the long-awaited fall debut of “Supergirl” (CBS, 8:30 p.m.).

Relative newcomer Melissa Benoist, 27, of Colorado was cast as Kara Zor-El, cousin of the more famous Earthly person from the planet Krypton almost exactly a year ago.

“I auditioned the day after Halloween last year, and it was a Saturday morning,” she told reporters at the TV Critics Association summer press tour.

“I think the second that I saw in my email inbox the title ‘Supergirl,’ I just knew automatically that it was something important and it was something exciting and rare and that I wanted to be a part of.”

It helps that the new series is from the same team that made “The Flash” and “Arrow” successful on the sister station.

And those producers said they liked what they saw in Benoist right away.

“Melissa was the very first person we saw for Kara,” says executive producer Andrew Kreisberg. “As soon as we saw her, we just knew she was the one. She had the strength, the hope, the heart, the humor, and just that instant likability, and [WB studio head] Peter Roth said after watching her that it was the closest feeling he’s had since he saw Christopher Reeve, and it really is the truth.”

“He said that?” Benoist said.

“We looked at each other and were blown away” by her audition, producer Ali Adler says. Still, she adds, “we had to see maybe a thousand more women. And we never stopped being in love with Melissa.”

When it came down to it, says yet another producer, Sarah Schechter, “nobody came close. She has the strength, the emotional depth, and the comedic chops to kind of do everything.”

Benoist says she was no comic book nerd when she was growing up.

“I never read ‘Supergirl,’” she says. “And I didn’t read too many of the other comics. But I loved Michael Keaton’s Batman. ‘Batman Returns’ is still one of my favorite movies.”

Nor was she particularly good at sports or other physical activities, she says.

“I would have moments where I felt confident and where I felt strong and brave and like I could do anything,” she says. “But then, like everyone else, I have a really, really awkward horribly awkward moments.”

Mostly in playing the role, Benoist says she has to keep in mind that Supergirl is a beacon of hope to others. ”I knew that her bravery and strength was so intrinsic and important to who she is and that I really needed to feel in myself in order to play that.”

It helped when she was called to fly.

“It’s really difficult,” she says of depicting that superpower. “There have been moments where I’m in that position and they’re like, ‘Try to look less concerned. You need to look comfortable.’ But actually, it’s also really exhilarating. As difficult as it is, it’s just as much, if not more, exciting to be to feel like you’re flying.”

And that’s what will win people over in the first episode, Kreisberg says — “just seeing the unfettered joy on her face as she’s flying around and as she’s reveling in this power, in this freedom.

“I think that there are a lot of heroes who are sort of very ambivalent about their powers and very dour, and we’re certainly guilty of putting some of those people on TV,” he says. “But one of the great joys of ‘Supergirl’ is that she really loves being Supergirl, and you see you only believe that and you only get that because Melissa loves being Supergirl.”

It’s catchy, says Calista Flockhart, who plays Cat Grant, Kara’s boss in “Supergirl.”

“It’s a real celebration of girl power,” says the former Ally McBeal. “It’s a great show for moms and daughters to watch together.”